Shadow Warrior 2 is in development, publisher Devolver Digital has confirmed today via Twitter.
A Facebook post on the Shadow Warrior page also points out to a website with the sequel's logo. There's literally no other information beyond the teaser-trailer and a silly question who reads "Who wants some more Wang?" reffering to the game's protagonist.
The post also suggests the sequel will be developed by Flying Wild Hog. Considering E3 is next week, we will probably hear more about the game then.
Shadow Warrior was released back in 2013, as a reboot of the classic '90s 3D-Realms shooter. It was a fast-paced violent FPS, and one would expect no less from the sequel. If you want to try the original, you can grab it on GoG, where it's currently 90% off.